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Evaluation of Alleviation Process of the Žilina Water Reservoir Focusing on Section Profiles

Project Summary :
Planned timetable: June 2008 - October 2008
Coordination (research) workplace: WRI Bratislava
Responsible researcher/coordinator: Ing. Katarína Holubová, PhD.
Co-researchers: Ing. Radoslav Čuban, RNDr. Zuzana Capeková

The aim of updating the data on capacity of the Žilina water work reservoir was assessment of sedimentation rate and determination of capacity curve, which would enable optimise manipulation order of using hydro-energetic power and also creation of conditions for effective protection of reservoir before negative effects of sedimentation process.

Digitálna ortofotomapa © GEODIS SLOVAKIA, s.r.o.
The distribution of cross sections along the Žilina water reservoir

For the evaluation process of sedimentation of the Žilina water reservoir measurement were used which WRI made in 2004 and the new measurement of 36 section profiles, which took place in 2008. Topography of the reservoir for both measurements has been processed in an application Surfer 8. The basis of the cross sections were designed, from which a grid 10 x 10 m was created.


Measurements  of section profiles in Žilina water reservoir (2008)

Based on the graphical interpretation of both measurements and their subsequent comparisons of sedimentation areas, possible erosion, thickness of sediments were evaluated.

Thickness of sediments created by the Žilina water reservoir for 3.5 years
(11-12/2004 and 06-08/2008)

The thickness of sediments which are created in the reservoir for a period of 3.5 years, are ranging from a few centimetres to about 100 cm. Considering the relatively high intensity and distribution of sediments in the reservoir, protective measures were proposed to the operator – baffle structures which would join to the two existing islands in the reservoir. Implementing these measures would allow creating favourable conditions for water flow, which would allow for smoother transport of sediments through the dam and would reduce sedimentation process.


Following the results of calculations of volumes an updated line of Žilina water reservoir volumes and line volumes for 2004 have been compiled. On the basis of volume differences in the amounts set out for 2004 and 2008 it was showed that in 2008 the total volume declined in comparison to the maximum operating level to 2004 in -551 080 m3, which represents a reduction of the initial amount of water reservoir in 3% over 3.5 years. Considering the volumes of sediments which were created in the reservoir for the period between the two measurements (3.5 years) is subject to the geological location of Žilina water reservoir (unstable flysch zone prone to erosion) as well as with respect to the reduced effectiveness of the above-lying reservoir Krpeľany the operator was recommended to have the measurements of the reservoir done again in up to 5 years.